Apparatus for forming internal teeth at large workpieces at a gear shaper

ABSTRACT

An apparatus for forming internal gear teeth at large workpieces at a gear shaper or gear shaping machine comprising a machine bed at which there are arranged a workpiece table for chucking a workpiece and an upright or stand. The workpiece table and the stand are rotatable, relative to one another, about the workpiece axis and radially feedable relative thereto. The stand has guide means along which there can be moved to-and-fro a plunger by means of a plunger drive. An auxiliary stand is rotatably and radially displaceable about the workpiece axis upon a bearing rim which is coaxially attached at the workpiece. The auxiliary stand has a guide arrangement along which there can be moved to-and-fro, in the tooth lengthwise direction of the internal teeth, an auxiliary plunger driven by the plunger by means of a bridge arrangement.

BACKGROUND OF THE INVENTION

The present invention relates to a new and improved construction ofapparatus for forming internal teeth at large workpieces at a gearshaping machine or gear shaper.

In its more specific aspects, the inventive apparatus for providinginternal gear teeth at large workpieces at a gear shaping machine,comprises a machine bed upon which there are arranged a workpiece tablefor chucking or clamping a workpiece and an upright or stand. Theworkpiece table and stand are rotatable, relative to one another, aboutthe workpiece axis and can be advanced or fed radially with respectthereto. The stand has guide means along which there can be movedto-and-fro a plunger by means of a plunger drive.

There are already known to the art gear shaping machines which,according to indexing techniques or part-rolling techniques, not onlycan fabricate external gear teeth, but also internal gear teeth, such asfor instance spline teeth for shaft-hub connections as well as couplingor clutch teeth, with great accuracy and surface quality. To fabricateinternal teeth the plunger, which carries the gear cutting tool, musthave a cantilever, in other words, must protrude a certain distance awayfrom the stand which is greater than one-half of the external diameterof the workpiece. In the case of workpieces of large diameter thiscauses difficulties, since if the plunger is extensively cantilevered,the machining forces exerted by the gear cutting tool, produceconsiderable bending moments at the plunger. Therefore, it is necessaryto either tolerate appreciable deformations of the plunger, and thus,attendant impairment of the accuracy and surface quality of the internalteeth, or else the plunger must be structured to be particularly sturdy,and thus heavy, increasing the cost of the entire gear shaping machineand its operating speed is lowered. Hence, such machine then no longeroperates economically when fabricating external gear teeth, and it isfor this reason that it was necessary to produce the external teeth andthe internal teeth of gears of large diameter at different machines. Thenecessity of rechucking or clamping the workpiece, when working atdifferent machines, again is associated with the drawback that, not onlyare there present time losses, but especially there cannot be preventedloss in accuracy of the arrangement, especially axial alignment, betweenthe internal teeth and the external teeth.

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind it is a primary object of thepresent invention to provide a new and improved construction ofapparatus for forming internal teeth at large workpieces at a gearshaper which is not associated with the aforementioned drawbacks andlimitations of the prior art proposals.

Another and more specific object of the present invention aims atproviding an apparatus for forming internal teeth at large workpieces,where it is possible, at heretofore known and existing gear shapingmachines having a non-cantilevered plunger or only a modestlycantilevered plunger, and therefore suitable only for producing externalteeth, to also fabricate central bores or hubs of large size gears withspline and/or clutch teeth.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the apparatus of the present development is manifested by thefeatures that an auxiliary stand is arranged rotatably and radiallydisplaceable about the workpiece axis upon a bearing rim securedcoaxially at the workpiece. This auxiliary stand has a guide arrangementor guide means along which there can be moved to-and-fro, in the teethlengthwise direction of the internal teeth of the workpiece, anauxiliary plunger equipped with a gear cutter tool. This auxiliaryplunger is driven by means of the aforementioned plunger through theintermediary of a bridge arrangement or bridge means.

With the inventive apparatus, which can be easily installed at existinggear shaping machines, the plunger drive moves, through the agency ofthe plunger and the bridge arrangement or bridge means, the auxiliaryplunger to-and-fro. This to-and-fro movement is generally a verticalup-and-down movement, since gear shaping machines for larger workpiecesgenerally are constructed such that the workpiece is chucked or clampedwith its axis extending vertically at the machine table, and sinceinternal teeth such as spline or clutch teeth formed at larger sizeworkpieces, usually are straight or linear teeth. However, the inventiveapparatus also can be structured such that there can be producedtherewith helical internal teeth. To this end, it is only necessary thatthe guide means at the auxiliary stand can be adjusted at an inclinationwith respect to the lengthwise axis of the workpiece, as such is knownfor guide means at stands for gear shaping machines and other gearprocessing machines.

All of the movements of the inventive apparatus, needed for fabricatinga tooth system, can be derived from drives which are provided anyway atthe gear shaping machine. This is particularly valid, first of all, asconcerns the displacement movements or strokes of the auxiliary plunger,which, as described, are generated by the plunger drive of the gearshaping machine. Moreover, the inventive bridge arrangement ensures thatthe auxiliary stand, and together therewith, the auxiliary plunger,participate in the radial feed or advance movements as well as also inthe indexing movements and possible generating movements of the stand inrelation to the workpiece table. The inventive apparatus therefore neednot be equipped with its own drive. Consequently, it is simple andnon-bulky in construction, and with appropriately low expenditure inwork can be installed, on the one hand, at a gear shaping machine, and,on the other hand, at the workpiece which has been chucked or clamped atthe machine table.

It is advantageous if the bridge arrangement or bridge means possesses adisplacement or sliding drive, controlled by the plunger movements, inorder to change the spacing of the auxiliary stand from the stand orupright. This displacement drive renders it possible to raise the gearcutting tool arranged at the auxiliary plunger, following each workstroke for the duration of the return stroke from the workpiece.Consequently, the tool can be protected and there can be producedinternal teeth of highest surface quality. The displacement or slidingdrive can not only be controlled by the plunger movements, butfurthermore, its drive force can be obtained by a reversing gearing ortransmission of known construction, for instance a spline gearing.According to preferred embodiments of the invention, the displacementdrive however has its own power source, for instance an electrical,pneumatic or hydraulic power source.

Although, for the reasons described herein, it is advantageous to beable to periodically alter the spacing between the auxiliary stand andthe stand, nonetheless the inventive bridge means also can beconstructed such that it rigidly connects the auxiliary stand with thestand of the gear shaping machine. This is possible, for instance, whenthe inner diameter of the internal gearing, which is to be fabricatedwith the inventive apparatus, is sufficiently large in order to renderpossible a pivotal arrangement of the gear cutting tool at the auxiliaryplunger, corresponding to the usual arrangement of the tool at theplunger of a gear shaping machine where the tool is pivoted away fromthe workpiece during each return stroke.

The inventive bridge means or arrangement can be structured such that itdirectly connects the auxiliary plunger with the plunger of the gearshaping machine. In this case, although the bridge means is loaded withbending moments by the machining or cutting forces, nonetheless bendingof the bridge means does not have any appreciable effect upon themachining accuracy, since the auxiliary plunger, with adequate sturdystructuring of the auxiliary stand and the components carrying such, issufficiently accurately guided.

According to preferred embodiments of the invention there are, however,avoided appreciable bending loads being applied to the bridge means andalso the remaining components of the inventive apparatus in that, thereis operatively associated with the bridge means a shaft which, on theone hand, is mounted at the stand, on the other hand, at the auxiliarystand. The shaft supports two pinions, of which the one meshes with agear rack arranged at the plunger and the other with a gear rackarranged at the auxiliary plunger. It is possible, with relativelylittle expenditure, to design the shaft to be sufficiently strong inorder to withstand the rotational moments or torques acting thereatwithout any appreciable torsion. Furthermore, even any significanttorsion of the shaft does not have any effect upon the auxiliary plungerand its guiding at the auxiliary stand.

If the bridge means is provided with a displacement or sliding drive,then the shaft is telescopically extendable. Hence, the displacementdrive either can be arranged at a rod which is essentially parallel tothe shaft and interconnecting the stand with the auxiliary stand or atthe shaft itself.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above, will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is a perspective view of a known gear shaping machine and aworkpiece and equipped with an apparatus constructed according to theinvention;

FIG. 2 is a perspective view of part of the apparatus of FIG. 1, lookingin the direction of the arrow II thereof;

FIG. 3 is a sectional view of the arrangement of FIG. 1 showing modifieddetails of the apparatus; and

FIG. 4 is a vertical sectional view of the arrangement of FIG. 1, takensubstantially along the line IV--IV thereof, showing further modifieddetails of the apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, the exemplary embodiment of gear shapingmachine or gear shaper, particularly as shown in FIG. 1, will be seen tocomprise a machine bed 10 upon which there is rotatably mounted aworkpiece table 12 about an essentially vertical axis A. Furthermore,upon the machine bed 10 there is displaceably guided a bed carriage orslide 14, in the direction of the double-headed arrow B, tangentiallywith respect to the workpiece table 12. Secured at the workpiece table12 is a workpiece 16 having a lengthwise axis. This workpiece 16 isshown provided with external teeth 16' and should be provided withinternal teeth 16". Displaceably guided upon the bed carriage 14 is astand or upright 18, movable in the direction of the arrows C and C'radially with respect to the workpiece table 12. At the stand or upright18 there is attached a plunger guide or plunger guide means 20 which isrotatably adjustable about a radial rotational axis in relation to theworkpiece table 12. The plunger guide or guide means 20, in theillustrated embodiment, has been shown vertically adjusted. At theplunger guide 20 there is attached an electric motor 22 or othersuitable drive. A spindle 24 is rotatably mounted at the plunger guide20, spindle 24 being in threaded meshing engagement with a plunger 26displaceable at the plunger guide 20. Also constituting part of the gearshaping machine is a not particularly visible drive arranged below theworkpiece table 12, by means of which this workpiece table 12 can berotated, in increments or steps of adjustable length, in the directionof the arrows E or in the opposite direction, these adjustableincrements or steps being accommodatable to the pitch of each of theteeth 16' and 16" of the workpiece 16.

What has been described above essentially corresponds to the standardconstruction of a gear shaping machine or gear shaper as is known in theart.

Now installed upon the workpiece 16 is an apparatus for fabricatinginternal teeth 16". As concerns this apparatus the same comprises abearing rim or collar 28, or equivalent structure, which is securedexactly coaxially with respect to the workpiece 16 and the workpiecetable 12 upon such workpiece. For attachment purposes there are used, byway of example, in the illustrated embodiment, threaded bolts 30 or thelike, extending through the bearing rim 28 and being threaded intosupport or contact plates 32. These support plates 32 are, for instance,welded or otherwise suitably affixed at the workpiece 16 and machined insuch a manner that, their upper faces or surfaces come to lie in acommon plane extending exactly perpendicular to the workpiece axis A. Atthe bearing rim 28 there is rotatably mounted, by means of extremelyprecise axial and radial bearings 34, a rotatable plate 36 about theworkpiece axis A. Upon the rotatable plate 36 there are secured twoguide rails 38 arranged perpendicular to and in spaced relationship fromthe workpiece axis A. These guide rails or rail members 38 guide anauxiliary stand carriage or slide 40 upon which there is secured anauxiliary stand 42.

Now there is guided in the guide or guide means 42' of the auxiliarystand 42 so as to be vertically displaceable an auxiliary plunger 44, atthe lower end of which there is attached a gear cutting or shaping tool46 in the form of a single hobbing tooth. Formed or attached at theauxiliary plunger 44 is a gear rack 48. Meshing with this gear rack 48is a pinion 50 which is attached at a shaft 52. This shaft 52 is mountedin the auxiliary stand or upright 42 at the neighborhood of the pinion50. In FIG. 4 there has been shown a radial bearing 54 and an axialbearing 54'.

The shaft 52, according to the showing of FIG. 1, possesses amulti-edge, typically a square portion 56, which is telescopicallydisplaceable in a tubular-shaped shaft section 58 of correspondinginternal shape or profile. The shaft section or piece 58 is mounted at atraverse or crossbar 60 which is displaceably guided at the plungerguide or guide means 20 and bridges the plunger 26, so that it does nothinder it during its up-and-down movements. By means of a clamping screw62 or other suitable or equivalent device, the traverse or crossbar 60is fixedly mounted at the plunger guide or guide means 20 at anelevational position which depends upon the thickness of the workpiece16. At the shaft section or piece 58 there is attached a pinion 64 whichmeshes with a gear rack 66 secured at the plunger 26. The up-and-downmotions, imparted to the plunger 26 by the electric motor 22 through theintermediary of the spindle 24, are thus transmitted by means of thegear rack 66, the pinion 64, the shaft 52, the pinion 50 and the gearrack 48 to the auxiliary plunger 44, so that such auxiliary plunger 44is moved always in the same direction and, since the pinion 64 and thepinion 50, in the illustrated embodiment, are identical, also moveup-and-down through the same distance or amount as the plunger 26.

According to the showing of FIGS. 1 and 2, a larger gear 68 meshes withthe pinion 50. This larger gear 68 is connected by means of a shaft 70,mounted at the auxiliary stand 42, with a cam disk 72. At thecircumference of the cam disk 72 there are attached two cams or dogs 74and 74' which control a valve 76 arranged at the auxiliary standcarriage or slide 40. The valve 76, in turn, controls lines or conduits78 and 78' which flow communicate a hydraulic pump 80 with adisplacement or sliding drive 82 constructed as a double-actingpiston-and-cylinder unit 82', 82".

With the exemplary embodiment according to the showing of FIGS. 1 and 2the cylinder 82' of the displacement drive or drive means 82 is securedat the auxiliary stand carriage or slide 40 and the related piston 82"is attached at a rod 84. The rod 84 extends essentially parallel to theshaft 52 and is secured at the traverse 60 at the piston rod end remotefrom the displacement drive 82.

Instead of providing this arrangement, a modification is shown in FIG. 3wherein the cylinder 82' of the displacement drive 82 is attached at thetraverse or crossbar 60, whereas the end of the rod 84, remote from thedisplacement drive 82, is secured at the auxiliary stand carriage 40. Inthis case there is provided, instead of the mechanically actuatablevalve or valve means 76, preferably an electromagnetically actuatablevalve or valve means 86. This valve 86 is directly secured at thetraverse 60 and can be actuated by the switches 88 and 88'. Theseswitches 88 and 88' are arranged at the plunger guide 20 and areactuated by the cams or dogs 90 and 90', or equivalent structure,adjustably fixed at the gear rack 66.

According to a further modification, as shown in FIG. 4, thedisplacement drive 82, likewise in the form of a piston-and-cylinderunit 82', 82", is arranged at the shaft 52 and there is dispensed withthe use of the rod 84. According to the showing of FIG. 4, it will beseen that at the shaft 52 there is attached an externallytoothed-coupling or clutch element 92 which, at the same time, isconstructed to form the piston 82" of the displacement drive 82. Thehollow shaft section or piece 58 mounted in the traverse 60 forms at thesame time the internally toothed-coupling or clutch element and isstructured so as to constitute the double-acting cylinder 82' and isconnected with the valve 86.

The apparatus for machining internal teeth, for the illustrated anddescribed embodiments, operates in the following manner: during eachdownward stroke of the plunger 26 the auxiliary plunger 44 likewisecarries out a downwardly directed work stroke, so that the gear cuttingor shaping tool 46 machines the internal teeth 16". As soon as the gearcutting tool 46 has moved downwardly, out of the internal teeth 16",then the cam or dog 74 of the arrangement of FIGS. 1 and 2 controllablyswitch the valve 76, or for the modified embodiments of FIGS. 3 and 4,the cam or dog 90 switch the valve 86, and thus, the displacement drive82 is pressurized in a manner such that it displaces the auxiliary stand42 in a direction away from the stand 18, through a distance which hasbeen indicated in FIG. 1 by the thin arrows F. At the end of the upwardstroke of the plunger 26 and the auxiliary plunger 44 the cams or dogs74' (FIGS. 1 and 2) and 90' (FIGS. 3 and 4), respectively, again switchthe valves 76 and 86, respectively, so that the displacement drive 82 ispressurized in the opposite direction and the auxiliary stand 42 isshifted back into its work position in the direction of the arrow F'.During the upward stroke the auxiliary stand 42 can be displaced in thedirection of one of the arrows C of FIG. 1, so that the gear cutting orshaping tool 46 carries out an advancing or feed movement. This feedmovement is accomplished in that, the stand 18 is shifted by means ofits standard feed drive, of which there has been shown in FIG. 1 thethreaded spindle 94 thereof, likewise through the directional distanceC, and thereby, by means of the rod 84, entrains the auxiliary standcarriage 40 together with the auxiliary stand 42. Thereafter, there isaccomplished the next work stroke of the auxiliary plunger 44. Afterthere has been finished hobbed, in this manner, following a certainnumber of work strokes, a tooth gap of the internal teeth 16" and thereis necessary an indexing movement of the workpiece 16, then the stand18, and together therewith the auxiliary stand 42, are moved backthrough a distance indicated by the arrows C' in FIG. 1, so that theworkpiece 16 can freely rotate below the apparatus for forming theinternal teeth.

While there are shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims. ACCORDINGLY,

What I claim is:
 1. An apparatus for forming internal teeth at largeworkpieces at a gear shaping machine, comprising:a machine bed; aworkpiece table for chucking a workpiece having a workpiece axisarranged at said machine bed; stand means arranged at said machine bed;said workpiece table and stand means being relatively rotatable withrespect to one another and relatively advanceable with respect to oneanother; said stand means comprising guide means; a plunger; a plungerdrive for moving said plunger to-and-fro along said guide means; anauxiliary stand; bearing means substantially coaxially secured at theworkpiece for mounting said auxiliary stand to be rotatable about theworkpiece axis and radially shiftable with respect thereto; an auxiliaryplunger arranged at said auxiliary stand; auxiliary stand guide meansfor guiding said auxiliary plunger; bridge means operatively coactingwith said plunger and said auxiliary plunger; and said auxiliary plungerbeing driven by said plunger through the agency of said bridge meanssuch that said auxiliary plunger moves along said guide means of saidauxiliary stand back and forth in the tooth lengthwise direction of theinternal teeth of the workpiece.
 2. The apparatus as defined in claim 1,wherein:said bearing means comprises a bearing rim coaxially secured atthe workpiece.
 3. The apparatus as defined in claim 1, furtherincluding:displacement drive means controlled by the movement of atleast one of said plungers for changing the spacing between theauxiliary stand and the stand means.
 4. The apparatus as defined inclaim 3, wherein:said displacement drive means has its own power source.5. The apparatus as defined in claim 4, wherein:said power sourcecomprises hydraulic pump means.
 6. The apparatus as defined in claim 1,wherein:said bridge means embodies at least one shaft having opposedends; said shaft having one end mounted at said stand means and itsother end mounted at said auxiliary stand; said shaft being providedwith two pinions; a first gear rack arranged at said plunger; a secondgear rack arranged at said auxiliary plunger; one of said pinionsmeshing with said first gear rack; and the other of said pinions meshingwith said second gear rack.
 7. The apparatus as defined in claim 6,wherein:said shaft is structured so as to be telescopically extensible.8. The apparatus as defined in claim 7, including:displacement drivemeans controlled by the movement of at least one of said plungers forchanging the spacing between the auxiliary stand and the stand means;said displacement drive means being arranged at rod meansinterconnecting said stand means with said auxiliary stand; and said rodmeans extending essentially parallel to said shaft.
 9. The apparatus asdefined in claim 6, including:a displacement drive means which isarranged at said shaft.
 10. The apparatus as defined in claim 3,wherein:said bridge means embodies at least one shaft having opposedends; said shaft having one end mounted at said stand means and itsother end mounted at said auxiliary stand; said shaft being providedwith two pinions; a first gear rack arranged at said plunger; a secondgear rack arranged at said auxiliary plunger; one of said pinionsmeshing with said first gear rack; the other of said pinions meshingwith second gear rack; and said shaft being structured to betelescopically extensible.
 11. The apparatus as defined in claim 4,wherein:said bridge means embodies at least one shaft having opposedends; said shaft having one end mounted at said stand means and itsother end mounted at said auxiliary stand; said shaft being providedwith two pinions; a first gear rack arranged at said plunger; a secondgear rack arranged at said auxiliary plunger; one of said pinionsmeshing with said first gear rack; the other of said pinions meshingwith said second gear rack; and said shaft being structured to betelescopically extensible.
 12. An apparatus for forming internal teethat large workpieces at a gear shaping machine comprising:a machine bed;a workpiece table for chucking a workpiece having a workpiece axisarranged at said machine bed; stand means arranged at said machine bed;said stand means comprising guide means; a plunger; a plunger drive formoving said plunger along said guide means; an auxiliary stand; meanssecured at the workpiece for mounting said auxiliary stand to berotatable about the workpiece axis and radially shiftable with respectthereto; an auxiliary plunger arranged at said auxiliary stand;auxiliary stand-guide means for guiding said auxiliary plunger; bridgemeans operatively coacting with said plunger and said auxiliary plunger;and said auxiliary plunger being driven by said plunger through theagency of said bridge means such that said auxiliary plunger moves alongsaid guide means of said auxiliary stand substantially in the toothlengthwise direction of the internal teeth of the workpiece.